(a) Field of the Invention
This invention relates to an improved corrosion inhibitor system, and more particularly, to an improved corrosion inhibitor system for an intermediate heat transfer medium used in indirect cooling processes.
(b) Description of the Prior Art
In the chemical industry, there are many requirements for cooling heat transfer units wherein heat exchanger assemblies are designed for corrosive products, high pressures, high viscosities and the like unsuited for a refrigeration condenser/evaporator system. Such indirect cooling of heat transfer units are based on the use of an intermediate heat transfer medium, such as salt-based brines, glycol base brines, organic based brines using methylene chloride acetone and the like, in an indirect heat transfer assembly wherein the intermediate heat transfer medium may be cooled in an evaporator of a refrigeration system or with cooling water or other cooling medium and heated in the unit operation or process requiring cooling. Indirect heat transfer cooling systems using brines as the intermediate heat transfer medium include corrosion inhibitor systems to reduce corrosion rates of the heat transfer surfaces.
Corrosion inhibitors for such intermediate heat transfer media have been based upon the use of chromate salts, phosphates, phosphonates, nitrites, acrylates and the maintenance of a high pH. Chromate salts are being eliminated as a result of toxic effects to the environment. All such corrosion inhibitor systems are of limited success, particularly when used in a calcium chloride based intermediate heat transfer medium.
Problems associated with such corrosion inhibitors include, inter alia, sludge formation, promotion of pitting, ineffective protection of metal surface and the like. There is the need for an improved corrosion inhibitor system with minimal formation of sludge and low corrosion rates.